﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Jenvin.Library.DataStruct
{
    /// <summary>
    /// hash 算法大集合
    /// 推荐使用FNV1算法
    ///  http://www.partow.net/programming/hashfunctions/index.html
    /// </summary>
    public sealed class HashAlgorithms
    {
        /// <summary>
        /// 加法hash 
        /// </summary>
        /// <param name="key">字串</param>
        /// <param name="prime">一个质数</param>
        /// <returns></returns>
        public static int AddHash(string key, int prime)
        {
            int hash = 0;
            foreach (char c in key)
            {
                hash += c;
            }
            return hash % prime;
        }
        /// <summary>
        /// 旋转hash
        /// </summary>
        /// <param name="key">字串</param>
        /// <param name="prime">一个质数</param>
        /// <returns></returns>
        public static int RotateHash(string key, int prime)
        {
            int hash = 0;
            foreach (char c in key)
            {
                hash = (hash << 4) ^ (hash >> 28) ^ c;
            }
            return hash % prime;
            //可使用下面的语句替代。hash % prime
            //return (hash ^ (hash >> 10) ^ (hash >> 20)) & mask;

        }
        /// <summary>
        /// MASK值，随便找一个值，最好是质数
        /// </summary>
        private static int M_MASK = 17;// unchecked((int)0x8765fed1);
        /// <summary>
        /// 一次一个hash
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int OneByOneHash(string key)
        {
            int hash = 0;
            foreach (char c in key)
            {
                hash += c;
                hash += (hash << 10);
                hash ^= (hash >> 6);
            }
            hash += (hash << 3);
            hash ^= (hash >> 11);
            hash += (hash << 15);
            //   return (hash & M_MASK);
            return hash;
        }
        /// <summary>
        /// Bernstein's hash
        /// </summary>
        public static int BernsteinHash(string key)
        {
            int hash = 0;
            foreach (char c in key)
            {
                hash = 33 * hash + c;
            }
            return hash;
        }

        /**
        * Universal Hashing
        */
        public static int UniversalHash(char[] key, int mask, int[] tab)
        {
            int hash = key.Length, i, len = key.Length;
            for (i = 0; i < (len << 3); i += 8)
            {
                char k = key[i >> 3];
                if ((k & 0x01) == 0) hash ^= tab[i + 0];
                if ((k & 0x02) == 0) hash ^= tab[i + 1];
                if ((k & 0x04) == 0) hash ^= tab[i + 2];
                if ((k & 0x08) == 0) hash ^= tab[i + 3];
                if ((k & 0x10) == 0) hash ^= tab[i + 4];
                if ((k & 0x20) == 0) hash ^= tab[i + 5];
                if ((k & 0x40) == 0) hash ^= tab[i + 6];
                if ((k & 0x80) == 0) hash ^= tab[i + 7];
            }
            return (hash & mask);
        }

        /**
        * Zobrist Hashing
        */
        public static int ZobristHash(char[] key, int mask, int[][] tab)
        {
            int hash, i;
            for (hash = key.Length, i = 0; i < key.Length; ++i)
                hash ^= tab[i][key[i]];
            return (hash & mask);
        }

        // LOOKUP3 
        // 见Bob Jenkins(3).c文件

        // 32位FNV算法
        private static int M_SHIFT = 0;
        /// <summary>
        ///  32位的FNV算法
        /// </summary>
        /// <param name="data">data 数组</param>
        /// <returns></returns>
        public static int FNVHash(byte[] data)
        {
            int hash = unchecked((int)2166136261L);
            foreach (byte b in data)
            {
                hash = (hash * 16777619) ^ b;
            }

            if (M_SHIFT == 0)
                return hash;
            return (hash ^ (hash >> M_SHIFT)) & M_MASK;
        }
        /// <summary>
        /// 改进的32位FNV算法1
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        public static int FNVHash1(byte[] data)
        {
            const int p = 16777619;
            int hash = unchecked((int)2166136261L);
            foreach (byte b in data)
                hash = (hash ^ b) * p;
            hash += hash << 13;
            hash ^= hash >> 7;
            hash += hash << 3;
            hash ^= hash >> 17;
            hash += hash << 5;
            return hash;
        }

        /// <summary>
        /// 改进的32位FNV算法1
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        public static int FNVHash1(string data)
        {
            const int p = 16777619;
            int hash = unchecked((int)2166136261L);
            foreach (char c in data)
                hash = (hash ^ c) * p;
            hash += hash << 13;
            hash ^= hash >> 7;
            hash += hash << 3;
            hash ^= hash >> 17;
            hash += hash << 5;
            return hash & 0x7FFFFFFF;
        }

        /// <summary>
        /// Thomas Wang的算法，整数hash
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int IntHash(int key)
        {
            key += ~(key << 15);
            key ^= ((key >> 10) & 0x00CFFFFF);//key>>>10
            key += (key << 3);
            key ^= ((key >> 6) & 0x0CFFFFFF);//key>>>6
            key += ~(key << 11);
            key ^= ((key >> 16) & 0x0000FFFF);//key>>>16
            return key;
        }
        /// <summary>
        ///  RS算法hash
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int RSHash(string key)
        {
            int b = 378551;
            int a = 63689;
            int hash = 0;

            foreach (char c in key)
            {
                hash = hash * a + c;
                a = a * b;
            }


            return (hash & 0x7FFFFFFF);
        }

        /// <summary>
        ///  JS算法
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int JSHash(string key)
        {
            int hash = 1315423911;
            foreach (char c in key)
            {
                hash ^= ((hash << 5) + c + (hash >> 2));
            }


            return (hash & 0x7FFFFFFF);
        }
        /* End Of JS Hash Function */

        /// <summary>
        ///  JS算法
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int PJWHash(string key)
        {
            int bitsInUnsignedInt = 32;
            int threeQuarters = (bitsInUnsignedInt * 3) / 4;
            int oneEighth = bitsInUnsignedInt / 8;
            int highBits = unchecked((int)(0xFFFFFFFF << (bitsInUnsignedInt - oneEighth)));
            int hash = 0;
            int test = 0;
            foreach (char c in key)
            {
                hash = (hash << oneEighth) + c;

                if ((test = hash & highBits) != 0)
                {
                    hash = ((hash ^ (test >> threeQuarters)) & (~highBits));
                }
            }
            return (hash & 0x7FFFFFFF);
        }
        /* End Of P. J. Weinberger Hash Function */

        /// <summary>
        /// ELF算法
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int ELFHash(string key)
        {
            int hash = 0;
            int x = 0;
            foreach (char c in key)
            {
                hash = (hash << 4) + c;
                if ((x = (int)(hash & 0xF0000000L)) != 0)
                {
                    hash ^= (x >> 24);
                    hash &= ~x;
                }
            }


            return (hash & 0x7FFFFFFF);
        }
        /* End Of ELF Hash Function */

        /// <summary>
        /// BKDR算法
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int BKDRHash(string key)
        {
            int seed = 131; // 31 131 1313 13131 131313 etc..
            int hash = 0;
            foreach (char c in key)
            {
                hash = (hash * seed) + c;
            }
            return (hash & 0x7FFFFFFF);
        }
        /* End Of BKDR Hash Function */

        /// <summary>
        /// SDBM算法
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int SDBMHash(string key)
        {
            int hash = 0;

            foreach (char c in key)
            {
                hash = c + (hash << 6) + (hash << 16) - hash;
            }
            return (hash & 0x7FFFFFFF);
        }
        /* End Of SDBM Hash Function */

        /// <summary>
        /// DJB算法 由 Daniel J. Bernstein 教授展示于新闻组 comp.lang.C 上，是最有效率的散列函数之一
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int DJBHash(string key)
        {
            int hash = 5381;

            foreach (char c in key)
            {
                hash = ((hash << 5) + hash) + c;
            }
            return (hash & 0x7FFFFFFF);
        }
        /* End Of DJB Hash Function */

        /// <summary>
        /// DEK算法 The Art Of Computer Programming Volume 3
        /// </summary> 
        /// <param name="key"></param>
        /// <returns></returns>
        public static int DEKHash(string key)
        {
            int hash = key.Length;

            foreach (char c in key)
            {
                hash = ((hash << 5) ^ (hash >> 27)) ^ c;
            }

            return (hash & 0x7FFFFFFF);
        }
        /* End Of DEK Hash Function */

        /// <summary>
        /// AP算法
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int APHash(string key)
        {
            int hash = 0;
            for (int i = 0; i < key.Length; i++)
            {
                hash ^= ((i & 1) == 0) ? ((hash << 7) ^ key[i] ^ (hash >> 3)) :
                                               (~((hash << 11) ^ key[i] ^ (hash >> 5)));
            }

             return (hash & 0x7FFFFFFF);
          //  return hash;
        }
        /* End Of AP Hash Function */

        /// <summary>
        /// JAVA自己带的算法
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public static int JavaHash(string key)
        {
            int h = 0;
            int off = 0;
            int len = key.Length;
            for (int i = 0; i < len; i++)
            {
                h = 31 * h + key[off++];
            }
            return h;
        }

        public unsafe int DotNetHash(string key)
        {
            fixed (char* charPtr = new String(key.ToCharArray()))
            {

                int hashCode = (5381 << 16) + 5381;
                int numeric = hashCode;
                int* intPtr = (int*)charPtr;
                for (int i = key.Length; i > 0; i -= 4)
                {

                    hashCode = ((hashCode << 5) + hashCode +

                                (hashCode >> 27)) ^ intPtr[0];

                    if (i <= 2)
                    {
                        break;
                    }

                    numeric = ((numeric << 5) + numeric +
                                (numeric >> 27)) ^ intPtr[1];
                    intPtr += 2;
                }
                return hashCode + numeric * 1566083941;
            }
        }



        private static uint[] crctab = new uint[] {
                                0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3, 
                                0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 
                                0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
                                0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5, 
                                0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 
                                0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
                                0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
                                0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 
                                0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433, 
                                0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01, 
                                0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 
                                0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, 
                                0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 
                                0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
                                0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, 
                                0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 
                                0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 
                                0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 
                                0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7, 
                                0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 
                                0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 
                                0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79, 
                                0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 
                                0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, 
                                0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, 
                                0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 
                                0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, 
                                0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 
                                0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 
                                0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, 
                                0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf, 
                                0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
        };
        public int Crc32Hash(String key)
        {
            int i = 0, hash = 0;
            for (hash = key.Length, i = 0; i < key.Length; ++i)
            {
                hash = (hash >> 8) ^ (int)crctab[(hash & 0xff) ^ key[i]];
            }
            return hash;
        }


        // Pearson's Hash
        public int PearsonHash(string key)
        {
            uint hash = 0;
            int i = 0;
            for (hash = (uint)key.Length, i = 0; i < key.Length; ++i)
                hash = crctab[hash ^ key[i]];
            return (int)(hash);
        }

        //// CRC Hashing，计算crc,具体代码见其他
        // ub4 crc(char *key, ub4 len, ub4 mask, ub4 tab[256])
        // {
        //   ub4 hash, i;
        //   for (hash=len, i=0; i<len; ++i)
        //     hash = (hash >> 8) ^ tab[(hash & 0xff) ^ key[i]];
        //   return (hash & mask);
        // }
    }
}
